The author starts from the institutional division between philosophy and theology introduced in Italy at the end of the national unification, to present the interpretation of Anselm of Canterbury developed by Sofia Vanni Rovighi (1908-1990) during her career and based on the premise of a substantial difference between these two forms of speculation. Vanni Rovighi reads the “philosophical” texts by Anselm in the light of this distinction inherited from Thomas Aquinas and strongly held by neo-Thomism, but she misses in this way Anselm’s very close dialogue with Augustin’s De trinitate, ready to translate its Trinitarian theology in a new awareness about man and human knowledge. An essential moment of the philosophical history of the West remains underestimated and this invites us to a further reflection on the historiographic repercussions of an excessive separation between philosophy and theology.